Numerical control device, numerical control method, and machine tool system

Abstract

A numerical control device (1) controls a machine tool (10) so as to perform machining, in a state in which a pressing part (40) of the machine tool (10) is pressed against a machining target (W), while moving the machining target (W) relative to a tool (52) of the machine tool (10). The numerical control device (1) is provided with at least one memory (3) and at least one processor (4). The memory (3) stores a target value of a magnitude of a force for pressing the pressing part (40) against the machining target (W). The processor (4) acquires a physical quantity relating to movement of the machining target (W), calculates an acting force that acts on the machining target (W) due to the movement, on the basis of the physical quantity, and calculates a correction amount of the force for operating the pressing part (40), on the basis of the target value and the acting force.

Description

Numerical control device, numerical control method, and machine tool system

[0001] The present disclosure relates to a numerical control device, a numerical control method, and a machine tool system.

[0002] In a machine tool such as an NC lathe, a method is known in which the chucking pressure of a chuck that grips a workpiece is calculated based on the maximum rotation speed of the workpiece read from a machining program (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 6-246585

[0004] In machine tools such as automatic lathes, machining conditions such as the rotation speed of the spindle supporting the workpiece may change significantly as machining progresses. In such cases, calculating the force to support the workpiece based on the most stringent machining conditions read from the machining program, as described above, does not necessarily result in the workpiece being supported with the optimal force during machining. Therefore, it is desirable for machine tools to be able to support the workpiece with the optimal force regardless of the movement of the workpiece.

[0005] One aspect of the present disclosure is a numerical control device that controls a machine tool so as to machine an object to be machined while moving the object relative to a tool of the machine tool while a pressing unit of the machine tool is pressed against the object to be machined, the numerical control device comprising at least one memory and at least one processor, wherein the memory stores a target value for the magnitude of a force with which the pressing unit is pressed against the object to be machined, the processor acquires physical quantities related to the movement of the object to be machined, calculates an acting force acting on the object to be machined due to the movement based on the physical quantities, and calculates a correction amount for the force with which the pressing unit is operated based on the target value and the acting force.

[0006] 7 is a schematic diagram showing the configuration of a numerical control device according to an embodiment of the present disclosure and a machine tool to which the numerical control device is applied. It is a diagram showing information stored in a memory of the numerical control device shown in FIG. 1. It is a diagram showing an example of forces acting on a tailstock and a workpiece when the spindle of the machine tool is accelerated or decelerated in the direction of the axis X. It is a block diagram conceptually subdividing the configuration of the numerical control device shown in FIG. 1 based on each function. It is a diagram showing an example of forces acting on a tailstock and a workpiece when the spindle of the machine tool is stationary in the direction of the axis X. It is a diagram showing changes in force F' when the driving force D is maintained constant in the operation of FIG. 3. It is a diagram showing force F' when the driving force D is changed in the operation of FIG. 3 by a numerical control method according to an embodiment of the present invention. It is a flowchart for explaining the numerical control method of FIG. 7. It is a modified example of the numerical control device of FIG. 1, and is a front view of a chuck illustrating a case where the spindle rotation speed is low when applied to control of a chuck of a spindle. It is a front view of the chuck in FIG. 9 illustrating a case where the spindle rotation speed is high.

[0007] A numerical control device 1, a numerical control method, and a machine tool system 100 according to an embodiment of the present disclosure will be described below with reference to the drawings. As shown in FIG. 1 , the machine tool system 100 according to the present embodiment includes a machine tool 10 such as an automatic lathe that processes a workpiece (a workpiece) W, and a numerical control device 1 that controls the machine tool 10.

[0008] 1 , machine tool 10 includes a bed 20, a headstock 30, a tailstock (pressing unit) 40, and a tool unit 50. The headstock 30 is disposed on the upper surface of the bed 20, and includes a chuck 31 that grips the outer peripheral surface of a cylindrical workpiece W, and a spindle 32 that rotates the workpiece W gripped by the chuck 31 about axis X. The headstock 30 also includes a spindle moving unit 33 that supports the spindle 32 so that it can move in a direction along axis X. In other words, the headstock 30 supports the workpiece W so that it can rotate about axis X and move translationally in the direction of axis X.

[0009] The tailstock 40 is disposed on the upper surface of the bed 20 on the opposite side of the headstock 30 with the workpiece W in between. The tailstock 40 includes a conical center 41 having an apex, and a movable part 42 to which the center 41 is attached, with the apex pointing toward the tip of the workpiece W. The tailstock 40 also includes a linear motion mechanism 43 that moves the movable part 42 to which the center 41 is attached along the direction of the axis X.

[0010] The linear motion mechanism 43 includes a servo motor 43 a, a ball screw 43 b connected to the rotation shaft of the servo motor 43 a and supported rotatably about an axis parallel to the axis X, and a nut (not shown) fixed to the movable part 42. The ball screw 43 b is engaged with the nut, and rotation of the ball screw 43 b about its axis can linearly move the movable part 42 to which the nut is fixed along the axis X. In other words, the movable part 42 supports the center 41 so that the apex of the center 41 moves on the axis X.

[0011] Furthermore, the servo motor 43a is torque controlled by the numerical control device 1, which will be described later, to cause the movable part 42 to follow the movement of the workpiece W in the direction of the axis X so as to press the apex of the center 41 against the tip of the workpiece W. As a result, the workpiece W being machined is supported by the spindle 32 and the center 41 while being pressed from both sides in the direction of the axis X, thereby stabilizing the rotation of the workpiece W about the axis X.

[0012] The tool unit 50 is supported on the bed 20 by a support member (not shown), and includes a main body 51 that is movable in the radial direction of the workpiece W, and a tool 52 attached to the tip of the main body 51. The operation of the main body 51 causes the tip of the tool 52 to come into contact with the outer peripheral surface of the workpiece W that is rotating around the axis X, thereby cutting the workpiece W.

[0013] As shown in FIG. 1, the numerical control device 1 includes an input device 2, a memory 3 having a volatile storage medium such as a RAM and a non-volatile storage medium such as a ROM, HDD, or SSD, and at least one processor 4 such as a CPU.

[0014] The input device 2 is configured, for example, with a keyboard, a touch panel, a serial interface such as USB, or a combination of these, and accepts input of various information by a user. Specifically, the input device 2 accepts input for setting the machining program P or for numerically controlling the machine tool 10 and executing predetermined machining on the workpiece W. The input device 2 also accepts input of the required supporting force (target value) F necessary to stably support the workpiece W, i.e., the force required to press the workpiece W against the center 41.

[0015] 2, the memory 3 stores a machining program P and a necessary supporting force F received by the input device 2. The memory 3 also stores a system program p1, an application program p2, a torque control program p3, a correction program p4, and an equation of motion E in advance.

[0016] The machining program P is a numerical control program in which a plurality of operation commands are arranged in order of execution to control the operation of each part of the machine tool 10 required to machine the workpiece W. Specifically, the machining program P is a program for rotating the spindle 32 supporting the workpiece W about the axis X, and for moving the workpiece W in the direction of the axis X while bringing the tool 52 into contact with the workpiece W, thereby performing a predetermined machining operation on the workpiece W.

[0017] The system program p1 and the application program p2 are core programs that perform the basic functions of the numerical control device 1.

[0018] The torque control program p3 is a program that controls the torque of the servo motor 43 a of the tailstock 40. More specifically, the torque control program p3 causes the servo motor 43 a to output a predetermined torque. In other words, the torque control program p3 is a program that moves the movable part 42 in the direction of the axis X so that the apex of the center 41 is always pressed with a constant force against the tip of the workpiece W moving in the direction of the axis X.

[0019] The correction program p4 is a program that corrects the magnitude of the current value supplied to the servo motor 43a by torque control in accordance with the movement of the workpiece W in the direction of the axis X. Specifically, as shown in Fig. 3, the correction program p4 acquires, from the machining program P, the acceleration (physical quantity) a of the workpiece W that is moved in the direction of the axis X by executing the machining program P. Furthermore, the correction program p4 calculates, based on the acquired acceleration a, an inertial force I (action force) that acts on the movable part 42 and the center 41 that follow the movement of the workpiece W in the direction of the axis X. Furthermore, the correction program p4 corrects the driving force D that moves the movable part 42 and the center 41 in the direction of the axis X based on the calculated inertial force I, the necessary supporting force F stored in the memory 3, and an equation of motion E, which will be described later.

[0020] 3, the equation of motion E is the equation of motion when the workpiece W, against which the center 41 is pressed by torque control, is moved in the direction of the axis X. In this case, since it is assumed that no frictional force or gravitational load acts on the movable part 42, the equation of motion E can be expressed by the following equations (1) and (2): I=-(m a) (1) D=F+I (2) Here, m is the mass of the movable part 42 and the center 41.

[0021] The processor 4 reads and executes a machining program P from the memory 3 in accordance with a system program p1 and an application program p2 stored in the memory 3. In addition, the processor 4 executes a torque control program p3 and a correction program p4 in conjunction with the execution of the machining program P.

[0022] 4 shows a block diagram conceptually dividing the numerical control device 1 based on the contents of various programs stored in the memory 3 executed by the processor 4. The control contents of the numerical control device 1 will be explained in more detail below using the block diagram shown in FIG. 4. The numerical control device 1 can be considered to include an input device 2, a control unit 61, an acquisition unit 62, and a calculation unit 63.

[0023] The control unit 61 is a conceptual functional block based on functions achieved by the processor 4 executing the machining program P and the torque control program p3. The control unit 61 controls the spindle 32 and the spindle movement unit 33 in accordance with the machining program P to rotate the workpiece W about the axis X and translate it in the direction of the axis X. The control unit 61 also brings the tool 52 into contact with the outer peripheral surface of the workpiece W that is rotating about the axis X and moving translationally in the direction of the axis X, thereby executing predetermined machining on the workpiece W.

[0024] Furthermore, the control unit 61 obtains the load torque acting on the rotation shaft of the servo motor 43a based on the current value fed back from a sensor (not shown) attached to the servo motor 43a in accordance with the torque control program p3. The control unit 61 then controls the magnitude of the current value supplied to the servo motor 43a so that the load torque becomes a predetermined constant value. As a result, the control unit 61 operates the movable unit 42 with a driving force D so that the force F' with which the workpiece W is pushed by the center 41 becomes the required supporting force F, as shown in FIG.

[0025] The acquisition unit 62 and the calculation unit 63 are both conceptual functional blocks based on the functions achieved by executing the correction program p4 by the processor 4. The acquisition unit 62 analyzes the operation commands for the workpiece W included in the machining program P, and acquires the acceleration a of the workpiece W moving in the direction of the axis X in a time series.

[0026] The calculation unit 63 calculates the equation of motion E stored in the memory 3 using the acceleration a of the workpiece W acquired by the acquisition unit 62 and the necessary support force F read from the memory 3. As a result, the calculation unit 63 calculates the correction amount of the driving force D that operates the movable part 42 based on the inertial force I acting on the movable part 42 and the center 41, which move in the direction of the axis X following the workpiece W.

[0027] Furthermore, the control unit 61 corrects the command value for torque control of the servo motor 43a based on the correction amount calculated by the calculation unit 63. That is, the control unit 61 corrects the magnitude of the current value supplied to the servo motor 43a in accordance with the movement of the workpiece W in the direction of the axis X, and adjusts the driving force D so that the force F' with which the center 41 pushes the workpiece W matches the required supporting force F.

[0028] A numerical control method using the numerical control device 1 according to this embodiment configured as described above will be described below. In the following, an example will be described in which the workpiece W, against which the center 41 is pressed, is moved from a stopped state in the direction of the axis X to a direction away from the center 41 along the axis X, as shown in Figures 3 and 5 .

[0029] First, when the workpiece W is stationary in the direction of the axis X, as shown in Fig. 5, the torque-controlled movable part 42 is also stationary in the direction of the axis X, and therefore no inertial force I in the direction of the axis X acts on the movable part 42. Therefore, the driving force D that operates the movable part 42 and the force F' with which the workpiece W is pressed by the center 41 are equal in value. Therefore, when the control part 61 operates the movable part 42 with a driving force D that is the same in magnitude as the required support force F, the center 41 is pressed against the workpiece W with a force F' that is the same in magnitude as the required support force F. This allows the workpiece W to be stably supported.

[0030] From this state, when the workpiece W is moved at an acceleration a along the axis X in a direction away from the center 41 as shown in Fig. 3, the torque-controlled movable part 42 also follows the workpiece W at an acceleration a. At this time, an inertial force I corresponding to the mass m of the movable part 42 and the center 41 and the acceleration a acts on the movable part 42 and the center 41. If the driving force D is maintained constant, as shown in Fig. 6, the force F' with which the workpiece W is pushed by the center 41 is reduced by the inertial force I compared to the driving force D of the movable part 42.

[0031] 7, in the numerical control method according to this embodiment, during the time period from t1 to t2 when the workpiece W and the movable part 42 are moving in the direction of the axis X, the driving force D is increased by the amount of the inertial force I acting on the movable part 42. In other words, in this numerical control method, the magnitude of the driving force D that operates the movable part 42 changes in accordance with the movement of the workpiece W, and therefore the fluctuations in the force F' with which the center 41 presses the workpiece W can be kept small.

[0032] Hereinafter, the method of correcting the driving force D in the numerical control method according to this embodiment will be described in more detail with reference to the block diagram shown in FIG. 4 and the flowchart shown in FIG.

[0033] First, the acquisition unit 62 acquires the acceleration a of the workpiece W moving in the direction of the axis X during machining based on the machining program P (step S1). In this case, the acquisition unit 62 acquires the acceleration a by analyzing the control command for controlling the position of the workpiece W in the machining program P, and therefore can accurately acquire the acceleration a of the workpiece W at each time during machining.

[0034] Next, the calculation unit 63 calculates the inertial force I acting on the movable part 42 and the center 41 at each time based on equation (1) assuming that the acceleration a of the movable part 42 at each time during machining is the same as the acceleration a of the workpiece W (step S2). The calculation unit 63 also calculates equation (2) at each time using the required support force F stored in the memory 3 and the calculated inertial force I. That is, the calculation unit 63 calculates a correction amount for the driving force D taking into account the inertial force I acting on the movable part 42 in accordance with the movement of the workpiece W in the direction of the axis X (step S3).

[0035] Then, the control unit 61 corrects the driving force D of the torque-controlled movable unit 42 by the correction amount calculated by the calculation unit 63, and operates the movable unit 42 with the corrected driving force D (step S4). As a result, regardless of the movement of the workpiece W during machining, the force F' with which the center 41 presses the workpiece W can be adjusted to the required supporting force F, and the workpiece W can be stably supported. Therefore, the machining accuracy of the workpiece W can be further improved.

[0036] In this embodiment, an example is given of a case where external forces such as frictional forces and gravitational loads do not act on the movable part 42, but instead, it may be a case where these external forces act on the movable part 42.

[0037] For example, if a frictional force occurs in relation to the movement of the movable part 42 in the direction of the axis X, the frictional force (acting force) can be taken into account in the equation of motion E stored in the memory 3. In other words, if it is assumed that the frictional force acting on the movable part 42 includes friction proportional to the speed of the movable part 42 and friction of a predetermined value, the above equation (2) can be modified to the following equation (3).

[0038] D=F+I+kv+f (3) Here, k is the coefficient of dynamic friction, v is the speed of the movable part 42, and f is a predetermined value of friction force acting on the movable part 42. Furthermore, when a load due to gravity acts on the movable part 42, a term corresponding to the magnitude of the load (acting force) due to gravity can be added to the above equation (3).

[0039] In addition, in this embodiment, the driving force D is corrected in consideration of the inertial force I acting on the movable part 42, which is calculated using the acceleration a of the movable part 42. Alternatively, the driving force D may be corrected in consideration of the moment (acting force) acting on the workpiece W when the tool 52 is pressed against the workpiece W.

[0040] 1, the moment acting on the workpiece W differs between when the tool 52 is pressed against a position on the workpiece W close to the chuck 31 and when the tool 52 is pressed against a position far from the chuck 31. This moment can be calculated from the distance in the direction of the axis X from the chuck 31 to the position on the workpiece W where the tool 52 is pressed.

[0041] Therefore, the moment acting on the workpiece W from the position where the tool 52 is pressed on the workpiece W can be calculated, and the magnitude of the driving force D of the movable part 42 can be corrected according to the calculated moment. This makes it possible to change the force supporting the workpiece W according to the distance from the chuck 31 to the point of contact between the workpiece W and the tool 52. That is, similar to the above embodiment, the workpiece W can be supported with a force according to the machining conditions.

[0042] Furthermore, in this embodiment, if the corrected driving force D exceeds a predetermined threshold value, for example, the strength limit value of the workpiece W, the movement of the workpiece W and the movable part 42 in the direction of the axis X may be stopped or slowed down. This makes it possible to prevent the center 41 from being pressed against the workpiece W with an excessive force that may damage the workpiece W.

[0043] In the above embodiment, the case where the driving force D that operates the movable part 42 of the tailstock 40 is corrected has been described. Instead, the present invention may be applied to a case where the driving force Dc that drives the chuck 31 that is provided on the main spindle 32 and that holds the workpiece (machined object) W is corrected.

[0044] 9, the chuck 31 has three jaws (pressing portions) 31a that are equally spaced apart in the circumferential direction and are radially movable in order to grip the cylindrical workpiece W from the radially outer side. The jaws 31a of the chuck 31 are driven by a hydraulic system (not shown). The numerical control device 1 controls the hydraulic system to generate a force for holding the workpiece W.

[0045] The processor 4 of the numerical control device 1 acquires the force Fc (required supporting force, target value) required to support the workpiece W and the mass mc of each jaw 31a of the chuck 31, which are written in the machining program P or stored in the memory 3. The processor 4 also acquires, for example, information written in the machining program P, a movement command for controlling the spindle 32, or information fed back from a sensor (not shown) provided on the spindle 32.

[0046] For example, the processor 4 acquires the required supporting force Fc and the mass mc of each jaw 31a of the chuck 31 stored in the memory 3. The processor 4 also acquires the radial distance Rc from the axis X to the center of gravity Oc of each jaw 31a of the chuck 31 based on the outer diameter dimension of the workpiece W described in the machining program P. The processor 4 also acquires the spindle rotation speed (physical quantity) ω fed back from the sensor.

[0047] The processor 4 calculates the driving force Dc to be applied to each jaw 31a using the acquired necessary supporting force Fc, mass mc, spindle rotation speed ω, and radial distance Rc from the axis X to the center of gravity Oc of each jaw 31a of the chuck 31 according to the equation of motion (4): Dc = Fc + Rc × ω ２ × mc=Fc+Sc (4) Here, Sc is the centrifugal force (action force) acting on each jaw 31 a of the chuck 31 .

[0048] The processor 4 controls the hydraulic system using the calculated driving force Dc, thereby allowing the spindle 32 to continue supporting the workpiece W with an appropriate gripping force even when a centrifugal force Sc acts on each jaw 31 a of the chuck 31 in a direction away from the workpiece W due to the rotation of the spindle 32.

[0049] For example, when the outer peripheral surface of the workpiece W supported by the chuck 31 of the spindle 32 is machined by the tool 52, the outer diameter of the workpiece W decreases as the machining by the tool 52 progresses. When the rotation of the spindle 32 is maintained at a constant speed, the peripheral speed of the workpiece W relative to the cutting blade of the tool 52 decreases, causing the machining conditions to fluctuate, and therefore the spindle rotation speed ω is increased as the machining progresses.

[0050] That is, even if the outer diameter of the workpiece W changes, by increasing the spindle rotation speed ω, the peripheral speed of the workpiece W relative to the cutting blade of the tool 52 can be maintained constant, and machining can be continued under uniform machining conditions. However, when the spindle rotation speed ω increases, the centrifugal force Sc acting on each jaw 31a of the chuck 31 gripping the workpiece W increases. As a result, the holding force Fc required to hold the workpiece W decreases, and it may become impossible to hold the workpiece W securely.

[0051] It is conceivable to set a larger holding force for holding the workpiece W in advance, anticipating a decrease in the required holding force Fc with an increase in the spindle rotation speed ω, but a larger holding force may cause problems such as deformation of the workpiece W. According to this embodiment, as shown in Fig. 9, the driving force Dc applied to the chuck 31 is changed in accordance with changes in the centrifugal force Fc with an increase in the spindle rotation speed ω, which has the advantage that the workpiece W can always be held with an appropriate required supporting force Fc.

[0052] In addition, since there is no need for a sensor such as a pressure sensor that directly detects the force with which the jaws 31a of the chuck 31 are pressed against the workpiece W, there is also the advantage that the cost of introducing a sensor can be reduced.

[0053] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these.

[0054] The following supplementary notes are further disclosed with respect to the above embodiments and modifications. (Supplementary Note 1) A numerical control device that controls a machine tool so as to machine a workpiece while moving the workpiece relative to a tool of the machine tool with a pressing unit of the machine tool pressed against the workpiece, the numerical control device comprising: at least one memory and at least one processor, wherein the memory stores a target value for the magnitude of a force pressing the pressing unit against the workpiece, and the processor acquires a physical quantity related to the movement of the workpiece, calculates an acting force acting on the workpiece due to the movement based on the physical quantity, and calculates a correction amount for the force that operates the pressing unit based on the target value and the acting force. (Supplementary Note 2) The numerical control device according to Supplementary Note 1, wherein the processor accepts input of the target value. (Supplementary Note 3) The numerical control device according to Supplementary Note 1 or Supplementary Note 2, wherein the processor acquires the physical quantity based on command information related to the movement. (Supplementary Note 4) The numerical control device according to Supplementary Note 1 or Supplementary Note 2, wherein the processor acquires the physical quantity based on feedback information from the workpiece or the pressing unit during the movement. (Supplementary Note 5) The numerical control device according to any of Supplementary Note 1 to Supplementary Note 4, wherein the physical quantity is at least one of the position, velocity, and acceleration of the workpiece during the movement. (Supplementary Note 6) The numerical control device according to any of Supplementary Note 1 to Supplementary Note 5, wherein the processor calculates a correction amount for the force that operates the pressing unit based on an equation of motion that describes the movement using the target value and the acting force. (Supplementary Note 7) The numerical control device according to any of Supplementary Note 1 to Supplementary Note 6, wherein the acting force includes centrifugal force or frictional force. (Supplementary Note 8) The numerical control device according to any of Supplementary Note 1 to Supplementary Note 7 ... processor limits or stops the operation of the workpiece and the pressing unit when the correction amount exceeds a predetermined threshold. (Supplementary Note 9) The numerical control device according to Supplementary Note 1, wherein the pressing unit is a tailstock pressed against one end of the workpiece or a jaw of a chuck pressed against the outer peripheral surface of the workpiece.(Supplementary Note 10) A numerical control method for controlling a machine tool so as to machine an object to be machined while moving the object relative to a tool of the machine tool with a pressing unit of the machine tool pressed against the object, the numerical control method including: acquiring a physical quantity related to the movement of the object to be machined, calculating an acting force acting on the object to be machined due to the movement based on the physical quantity, and calculating a correction amount for the force that operates the pressing unit based on a target value of the magnitude of the force pressing the pressing unit against the object to be machined and the acting force. (Supplementary Note 11) A machine tool system comprising the numerical control device according to Supplementary Note 1 and the machine tool.

[0055] REFERENCE SIGNS LIST 1 Numerical control device 3 Memory 4 Processor 10 Machine tool 31a Claw (pressing part) 40 Tailstock (pressing part) 52 Tool 100 Machine tool system a Acceleration (physical quantity) E Equation of motion F, Fc Required support force (target value) W Workpiece (machined object) ω Spindle rotation speed (physical quantity)

Claims

1. A numerical control device that controls a machine tool so that a pressing unit of the machine tool is pressed against a workpiece while the workpiece is moved relative to a tool of the machine tool to perform machining, the numerical control device comprising at least one memory and at least one processor, wherein the memory stores a target value for the magnitude of the force with which the pressing unit is pressed against the workpiece, and the processor acquires physical quantities related to the movement of the workpiece, calculates an acting force acting on the workpiece due to the movement based on the physical quantities, and calculates a correction amount for the force that operates the pressing unit based on the target value and the acting force.

2. The numerical control device according to claim 1, wherein said processor accepts an input of said target value.

3. The numerical control device according to claim 1 or 2, wherein the processor acquires the physical quantity based on command information relating to the movement.

4. The numerical control device according to claim 1 or 2, wherein the processor acquires the physical quantity based on feedback information from the moving workpiece or the pressing unit.

5. A numerical control device according to any one of claims 1 to 4, wherein the physical quantity is at least one of the position, velocity, and acceleration of the moving workpiece.

6. A numerical control device according to any one of claims 1 to 5, wherein the processor calculates the correction amount of the force that operates the pressing unit based on an equation of motion that represents the movement using the target value and the acting force.

7. A numerical control device according to any one of claims 1 to 6, wherein the acting force includes centrifugal force or friction force.

8. A numerical control device according to any one of claims 1 to 7, wherein the processor limits or stops the operation of the workpiece and the pressing unit when the correction amount exceeds a predetermined threshold value.

9. A numerical control device according to claim 1, wherein the pressing portion is a tailstock pressed against one end of the workpiece, or a jaw of a chuck pressed against the outer peripheral surface of the workpiece.

10. A numerical control method for controlling a machine tool so that a pressing unit of the machine tool is pressed against a workpiece while the workpiece is moved relative to a tool of the machine tool to perform machining, the numerical control method comprising: acquiring a physical quantity related to the movement of the workpiece; calculating an acting force acting on the workpiece due to the movement based on the physical quantity; and calculating a correction amount for the force that operates the pressing unit based on a target value for the magnitude of the force pressing the pressing unit against the workpiece and the acting force.

11. A machine tool system comprising the numerical control device according to claim 1 and the machine tool.

Images